There are three types of muscle fiber present in voluntary muscle tissue (the muscle fibers to move the skeleton).   1: Fast-twitch fiber 2: Medium-twitch fiber 3: Slow-twitch fiber. Muscle fibers are highly plastic – in other words, they can alter their characteristics according to the type of exercise you perform. This means you can make all of these muscle fibers work to help you mold your physique.

Fast-twitch fiber: the strength muscle- When you swing a golf club, lift a weight, throw a ball or sprint, you recruit fast-twitch fibers. These fibers contract quickly, providing short bursts of energy required for explosive movements. This type of muscle fiber does NOT burn fat. Instead, the primary energy source for fast-twitch muscle fibers is blood sugar stored in the muscle cells themselves, as well as in the blood and liver. The fast twitch muscle fiber is a strength muscle, this energy source is quickly depleted, which is why a sprinter must rest after 50 to 100 yards and a bodybuilder must rest between each set. In fact a fast-twitch muscle fiber will give out after 30 to 60 seconds of continuous contraction. This is not the muscle fiber you want to call on to lose fat or get any type of endurance energy.

Medium Twitch-Fibers: the everyday muscle- This is very similar to fast-twitch fiber, in that it is also involved in explosive types of activity. However it is also capable of longer periods of activity. It doesn’t have quite the strength capacity of the fast-twitch fiber. When you use many of the cardio machines in the gym, take aerobics classes, or play basketball, you’re using medium-twitch fibers. Medium-twitch fiber burns sugar: it does NOT burn fat. Medium-twitch fiber can be developed through resistance-training and body-sculpting exercises.

Slow Twitch-Fibers: the fat burning muscle- For fat burning, slow-twitch fiber takes on a more dominant role. This is the kind of exercise you should do while on HCG. This type of fiber gets most of its energy from burning fat for fuel, in conjunction with oxygen, contracting very slowly but having the ability to endure over extended periods of activity. Slow-twitch fiber is very fatigue-resistant. This fiber has only a limited ability to increase in size, and as such little, if any muscular growth can take place.

They utilize body fat as fuel, burning it during a process known as the Krebs cycle. Through the Krebs cycle, your body metabolizes fat into energy. Basically, the goal in long, slow, distance exercise is to use as much slow-twitch fiber as possible, for as long as possible, so you can accelerate the rate at which your body burns fat.   Walking, running and cardio with no resistance are slow Twitch-Fiber exercise that will be fine to participate in while on HCG.